Plate holder for chromium-plating machines



Feb. 18, 1930. w. s. EATON PLATE HOLDER FOR CHROMIUM PLATING MACHINES Filed Jan. 8, 1927 OOOOOOOOOOOOOOO I l l l I I I l l l I I I I l l l l lll Y OOQQOOOOOOQOOOO ZWW ATTORNEY Patented Feb. 18, 1930 UNITED STATES WILLIAM S. EATON, F SAG HARBOR, NEW YORK PLATE HOLDER FOR CHROMIUM-PLATING MACHINES Application filed January 8, 1927. Serial No. 159,801.

My invention relates to plate holders for chromium plating machines, and more'particularly to a plate holder so constructed that the position in the plating bath of a plate or plates thereon during the plating operation may be so changed as to ensure a uniform deposit of the chromium upon different portions of the plate or plates carried thereby.

In chromium plating, the flow of the electric current from the anode to the object to be plated, acting as a cathode, while causing chemical reactions resulting in the reduction of chromic acid and the deposit of metallic chromium upon the cathode, liberates hydrogen from the solution, which hydrogen adheres to the cathode until bubbles of sufficient magnitude have been formed to cause them to break from the surface to which they adhere and pass upwardly from the solution. I have found it advantageous in chromium plating to keep the plates being coated as free from hydrogen as possible, the reducing action of the hydrogen apparently occuring while the hydrogen is in a nascent state. I r have found that even where a very slight obstruction along the surface of the plate or plates is present, at this point there is a failure to properly deposit chromium upon the cathode. This cannot be attributed to the slight dilference required in the throw of the metal during the plating operation, and the distances in some instances have varied so slightly that the difiiculty cannot be attributed to any variance in the resistance of the bath at this point. I believe this difficulty arises from the accumulation of hydrogen at such a point. I have also found that electrolytic action in diiferent portions ofthe bath seems to vary slightly either as a result of chemical reactions in'the bath or as a result of variance in the resistance in the members of the electrolytic couple.

Whatever the cause of the difficulties, I have been able to correct the conditions by changing the position of the articles in the bath from time to time during the plating operation, and by my present invention have provided a holder by means of which this change of position of the plates or other articles in the bath may be quickly and conveniently accomplished, the plate holder in its entirety being removed from the bath while adjusting the holder to secure the desired change of position of the plates or other objects carried thereby.

In the holder embodying the invention, the plate or plates are held in what may be termed a chuck of electroconductive material, which is supported from a terminal bar in a manner not only to permit movement thereof, but to conduct the electric current thereto and therethrough to the plate in a manner to secure approximately uniform resistance in the flow of the current to adjacent the edges of the chuck, the bulk of metal in the chuck and in the terminal bar being such as to offer no material resistance to the current at any point.

The terminal bar is provided with means permitting the convenient mounting and withdrawal of the holder in its entirety from the plating bath, and is also provided with adjustable means by which a plate or plates may be firmly secured to the chuck,'which means is of electroconductive material and assists in maintaining the plate at a substantially uniform potential throughout.

While the manner of revolubly mounting the chuck upon the terminal bar is simple,. nevertheless it ensures the desired electric contact between the terminal bar and the back plate of the chuck necessary for an efficient operation of a plating machine.

The invention consists primarily in a plate holder for chromium plating machines embodying therein a metallic back plate, a terminal bar electrically connected with said back plate, means revolubly mounting said back plate in relation to said terminal bar and means carried by said back plate adjacent the point of said last named means, whereby objects to be plated may be mounted upon said plate, and in such other novel features of construction and combination of parts as are hereinafter set forth and described, and more particularly pointed out in the claims hereto appended.

Referring to the drawings,

Fig. 1 is a side view of a plate holder embodying the invention partly broken away and shown in connection with an electric diagram and a fragmentary portion of atank for the plating bath;

F ig. 2 is a front view of the holder; and

Fig. 3 is an enlarged detail sectional view of the upper portion thereof upon an enlarged scale with parts broken away.

Like letters refer to like parts throughout the several views.

In the embodiment of the invention shown in the drawings, a indicatesa tank for the plating bath, 0 a bus bar carried by and insulated from said tank, 0 an electric generator, and cl a pole changing switch of the usual construction. These parts are shown merely as illustrating the mode of operation of a plate holder embodying the invention, and form no part of the present invention.

The tank a is provided with an insulating lining and with an insulated member 6 cooperating with this lining and supporting the plate holder in the bath.

The plate holder proper comprises a substantially rectangular metallic back plate f havingtherethrough parallel rows of openings f by means of which a lower clamp bar 9 may be mounted in any desired position in relation to the center of said plate by means of screws 9 fastened through said bar and cooperating with screw threads in the openings f.

Also adjustably mounted in relation to said back plate is a second bar It having openings therethrough to receive screws h which also co-operate with the screw threaded openings f to permit the adjustment of the bar it togvard or from the center of the plate 7 and the ar g.

Movably mounted in relation to the bar h" is a clamp bar 2' having a plurality of headed slides z" passing through openings 7& in the bar 72..

Mounted in the bar it and acting against the clamp bar 2' are a plurality of set screws by means of which the bar 2' may be forced toward the bar 9 in a manner to firmly clamp a plate or plates k in position with relation to the back plate 7 so that these plates will be in electrical connection at the top and bottom edges thereof with the bars 2' and g and throughout the back thereof with the plate f.

The electrical current is conducted to the plate 7, and therethrough to the bars 9, h and thy a terminal bar m, the plate f being pivotally mounted in relation to said terminal bar by means of a pivot screw it positioned substantially centrally of said plate and passing through said bar, a thumb nut n being used to clamp the plate when it has been set to any desired position against the terminal bar in a manner to ensure a sufficiently tight fit to avoid the development of resistance to the flow of the current at this point through the seepage of the electrolyte between said bar and the back plate To stiffen the plate f adjacent the pivot screw it and at the same time increase the bulk of the metal of the plate adjacent its point of contact with the terminal bar, I provide reinforcing metallic plates 7 and f connected with the plate 7 and extending from its point of pivotal support toward all edges of the plate. These plates f and f also serve to space the plate f sulficiently away from the terminal bar m to permit a free turning movement of this plate in its entirety. The terminal bar m is provided with a forked bracket 0, the downwardly extending arms 0 and 0 of which are adapted to straddle the insulating lining a of a tank, and the insulating support 6 at the top of the tank, and thus hold the plate in the tank, the pivot screw or thumb nut, in conjunction with this offset forked bracket 0 serving to hold the plate in its entirety with the face thereof in a substantially vertical plane.

The terminal bar m is in electrical connection with the source or generator 0 through the switch (Z and a conductor wire d. The bus bar Z) is similarly connected with the source by the lead (1 and a tank not shown is connected in like manner with said source through the lead (la. The manner of wiring is such that the polarity of the current passing to the terminal bar may be either minus or plus according to whether it is desired to deposit chromium upon plates carried by the holder or to strip the chromium therefrom.

lVhen it is desired to deposit chromium, the bus bar I) will have suspended therefrom anodes b, but the tank used for stripping has no anodes, one wall of the tank being uncovered and acting as a cathode. Y

The operation of the herein, described holder is substantially as follows lVhen it is desired to deposit chromium electrolytically, one or more plates or dies is are mounted upon the back plate f, the clamp bar 9 and upper bar it first having been adjusted to bring the central point of the plates or dies, or of a single plate or die, approximately at the center of the back plate 7. The thumb nut it before placing the holder in the tank, is used to draw the plates f, f and f in close electrical contact with the terminal bar m, the plate f being setwith opposite edges thereof in a horizontal plane. lVhen the clamp bar 9 in a manner to firmly secure the plates or dies in position by means of the set screws j, the holder is inserted in the bath, the forked bracket 0'0 being used to suspend same from the edge of the tank by means of the insulating lining of the tank and the member 6. The switch kl is then thrown so as to cause the current to flow through the lead d and the anode Z) to the plate holder,

the return being through the lead (l'.

W'hile the plates or dies upon the holder will be completely submerged in the bath in the tank a, the rate of deposit appears to be lower toward the bottom of the tank than toward the top thereof, and as heretofore stated, at the parting between difierent plates or dies when two or more are used upon the holder, there is a tendency, if there is any variation in the thickness of the plates or dies, of an interference with the electrical action resulting from the pocket caused by this variance in thickness at such parting. Since other portions of the thinner plate will receive a uniform deposit of chromium, I attribute this result to the presence of free hydrogen in this pocket, although it might occur as a result of even a slightly increased resistance at this point as compared with the resistance at .the edge of the thicker plate or die. I believe, however, that it is due to the presence of free hydrogen, since changing the position of the plate in the bath hasbeen found to correct the condition. This changing of the position of the plate, I also find is beneficial so far as the quality of the deposit is concerned, and by quality I have reference to the uniform depositing of the metal. This is probably due to the phenomena above referred to, characterized by the tendency of a more rapid deposit toward the topof the bath. lVhatever the causes, I have found it highly desirable at short intervals to remove the plate holder from the bath, loosen the thumb screw n, turn the plate f and its appurtenances 90 in arc, and after resetting the thumb nut, replacing the holder and the plates in the bath. By this practice not only is the major portion of each plate. during a part of the time required for depositing, brought within the upper portion of the bath. but the position of any pockets or any irregularities at or on the surface of the plates is so changed as to obviate those conditions, whatever they may be, which prevent, or tend to prevent the deposit of the chromium adjacent thereto. This shifting of the plates 7' need not be at frequent intervals. For example, if the plating operation is to take an hour, the plate holder may be turned at intervals of fifteen minutes. On the other hand, it may be turned more frequently, if desired, it being desirable, however, to allow the electro depositing to go on for substantially equal intervals with each position of the plate holder. I posit will rarely exceed .0008 of .aninch, it is apparent that any irregularities in this thick- Since the maximum deness of deposit due to any variance in the time interval will be so small as to have no appreciable effect whatever even with the finest printing plates.

The time required to strip a plate is so small that shifting of the plate holder need not be resorted to.

In the accompanying drawings, I have shown the invention reduced to its simplest form, which form I have found to give highly satisfactory results. It is not my intention, however, to limit the invention to this particular form, since it is apparent that such may be varied while preserving all of the essential characteristics of the invention.

Having described the invention, what I claim as new and desire to have protected by Letters Patent, is 2- 1. A plate holder for chromium plating machines embodying therein a metallic back plate, a terminal bar electrically connected with said back plate, means revolubly mounting said back plate in relation to said terminal bar and means carried by said back plate adjacent the point of said last named means, whereby objects to be plated may be mounted upon said plate.

2. A plate holder for chromium plating machines embodying therein a metallic back plate, a terminal bar, a pivot screw carried by said back plate and revolubly mounted in said terminal bar, whereby said back plate may have its position shifted in relation to i said bar and in the same vertical plane, a nut co-operating with said screw and said terminal bar whereby said back plate may be drawn into close electrical contact with said bar and held against movement, or said back plate may be disengaged from said terminal bar to permit rotary movement of said back plate and means carried by said-back plate adjacent the point of said last named means, whereby objects to be plated may be mounted upon said plate. 7

3. A plate holder for chromium plating machines embodying therein a metallic back plate having parallel rows of openings therethrough, a lower clamp bar, means co-operating with said bar and the openings in said back plate whereby said bar may be adjusted toward or from the center of the plate, a second bar, means co-operating therewith and with the openings in said back plate, whereby said second bar may be adjusted toward'or from said first named clamp, a clamp bar slidably mounted in relation to said second bar, set screws carried by said second bar and operative upon said last named clamp bar, a terminal bar electrically connected with said back plate, and means revolubly mounting said back plate in relation to said terminal bar.

4. A plate holder for chromium plating machines embodying therein a metallic back plate having parallel rows of openings therethrough, a lower clamp bar, means co-operating with said bar and the openings in said back plate, whereby said bar may be adjusted toward or from the center of the plate, a second bar, means co-operating therewith and with the openings in said back plate, whereby said second bar may be adjusted toward or from said first named clamp, a clamp bar slidably mounted in relation to said second bar, set screws carried by said second bar and operative upon said last named clamp bar, a terminal bar. a pivot screw carried by said back plate and revolubly mounted insaid terminal bar. whereby said back plate may have its position shifted m relation 'to said bar and in the same verticabplane, and a nutco-operating with said screw and said terminal bar whereby said back plate may be drawn into close electrical contact with said bar and held against movement,- or said back plate may be disengaged from said terminal bar to permit rotary movement of said back plate.

5. A plate holder for chromium plating machines embodying therein a metallic back plate. means whereby the objects to be plated may be mounted thereon, a terminal bar electrically connected with said back plate, means revolubly mounting said back plate in relation to said terminal bar, and reinforcing metallic plates connected with said back plate and extending from said means revolnbly mounting said back plate toward all edges of said back plate.

6. A plate holder for chromium plating machines embodying therein a metallic back plate, means whereby the objects to be plated may be mounted thereon, a terminal bar, a pivot screw carried by said back plate and revolubly mounted in said terminal bar, whereby said back plate may have its position shifted in relation to said bar and in the same vertical plane, a nut co-operating with said screw and said terminal bar whereby said back plate may be drawn into close electrical contact with said bar and held against movement, or said back plate may be disengaged from said terminal bar to permit rotary movement of said back plate, and reinforcing metallic plates connected with said back plate and extending from said means revolubly mounting said back plate toward all edges of said back plate.

7. A plate holder for chromium plating machines embodying therein a metallic back plate. means whereby the objects to be plated may be mounted thereon, a terminal bar, a

pivot screw carried by said back plate and revolubly mounted in said terminal -bar, whereby said back plate may have its position shifted in relation to said bar and in the same vertical plane, a nut co-operating with said screw and said terminal bar whereby said back plate maybe drawn into close electrical contact with said bar and held against move- WILLIAM S. EATON. 

